DIELECTRIC-PROPERTIES OF LI-EXCHANGED MIXED FE-CR OXIDE PILLARED PHOSPHATE()

The dielectric properties of mixed Fe-Cr oxide-pillared cr-zirconium p hosphate and derivatized Li+-exchanged have been studied by impedance spectroscopy. The pure Fe-Cr pillared material exhibits low electronic conductivity and presents only a dielectric relaxation. However, the Li+-exchanged sample is an ionic conductor and subtracting the de cont ribution, a dielectric relaxation at low frequency is observed. The Li + ions distribution presents a two-potential-well system; the ions loc alized at small pores cannot be displaced over long distances and thei r short hopping transitions determine the dielectric properties. On ot her hand, only a fraction of the ions located in large pores are free and can be displaced over long distances and the remainders are fixed and can only make short displacements. These ions behave like jumping dipoles and produce a dielectric relaxation at low frequencies and hig h temperatures. (C) 1997 Elsevier Science S.A.